Summaries
The Storm Warning Service (SVSD)
The Storm Warning Service (SVSD), instituted
in 1931, warns the management of the sea
defense structures when high water levels are
to be expected. After the sormflood disaster of
953 the procedures were modernized; since
then the task and the responsibility of
Rijkswaterstaat have been enlarged. The
decision to issue a warning now is entirely up to
Rijkswaterstaat although the KNMI (Royal
Netherlands Meteorological Institute) still
advises and makes prognoses. Because the
water-levels along the coast vary, the coastal
area has been divided into five sections for the
SVSD warning procedure.
Every section can be considered separately
now. Depending on the seriousness of the
situation telegrams can be forwarded for a
limited or a more extended dike-surveillance. If
necessary an emergency warning system can
be used.
Aprons for the storm-surge barrier in the
Oosterschelde
The aprons dumped on both sides of the
storm-surge barrier in the Oosterschelde form
that part of the sea bed protection that must
withstand the most severe wave- and
ilow-attacks. The construction to be made will
be a combination of the selected 'open' and
'closed' variety. The transition from the actual
apron into the sill will consist of an open filter
construction, whereas the remaining part will
consist of a bituminous mat, 32 centimeters thick,
covered with rubble (60/300 kilograms).
In the meantime part of the closed apron,
ocated on the Oosterscheldeside near the
Room pot-gap was laid by the asphalt ship 'Jan
Heymans'.
Soundings for the storm-surge barrier in the
Oosterschelde
Whpn the construction of the storm-surge
barrier is in progress high demands will be
made on the survey section in that area;
accurate and frequent soundings must be made
of the condition of the sea-bed to prevent that
the barrier itself or the coastal defenses in its
vicinity will be endangered by erosion of the
sea-bed.
Apart from the sounding equipmentfor
soundings the survey-vessels will need
instruments to define their position.
Due to the many objects and vessels in the
closure gaps no optical means to determine
positions are to be used. A radiographic
installation will be put on board of each
survey-vessel.
For a quick processing and presentation of
sounding data the appliances on board the
ships will be modernized.
The instrumentation of the inlet-sluice in the
Volkerakdam
The inlet-sluice in the Volkerakdam acts in
conjunction with the Haringvliet sluices, as a
regulator for the water management in the
northern Delta area. Temporarily, the sluice also
has another function. It combats the salt load
discharge on the fresh water Hollands Diep via
the locks in the Volkerakdam.
To be able to quickly establish the discharge of
the inlet-sluice and its impact on the salinity of
the Volkerak, an automatic measuring net has
been installed in and in the vicinity of the sluice.
By means of the instruments information can be
gathered about the water-level, the position of
the sluice-gates, the salinity and the
temperature of the water. These data can be
evaluated and pushed on to various stations like
the Volkerakdam control office, the
Hellevoetsluis survey station and the
Dordrecht-office.
Hydraulic research for the Philipsdam
The system that separates the salt water from
the fresh water in the Philipsdam locks will be
an improved version of the Kreekrak locks,
which locks were the prototype actually. The
system in question must try and as much as
possible limit the borderlayer between the salt
and fresh water. Improvements could be made
in this respect by changes in the construction of
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